Tensioning element, in particular for the suspension of building components, and also a method for the manufacture thereof

ABSTRACT

A tensioning element ( 1 ), especially for the suspension of building components, is provided with a number of wires ( 3 ) arranged approximately in parallel forming a wire cable ( 2 ). These wires ( 3 ) are anchored at each end in an end piece ( 6 ) absorbing the tensile forces exerted on the wire cable. The end piece ( 6 ) is at least partly provided with a plastic deformable sheath ( 6   b ) which serves to house one end of a wire cable, where this sheath ( 6   b ) is compressible with the end of the wire cable. This enables rapid anchoring of the wire cable in the end piece and this guarantees a high breaking load.

[0001] The invention concerns a tensioning element, in particular for the suspension of building components, with a number of wires arranged in parallel forming a wire cable, the ends of said wires each being anchored in an end piece absorbing the tensile forces exerted on the wire cable, and also a method for the manufacture thereof.

[0002] Tension braces made from high tensile strength wires which are used in construction for the suspension of building components, for example as stay cables for cable-stayed bridges, for the tensioning of roofs and for other purposes, allow an optically light, filigree node of construction and are also advantageous in terms of assembly techniques since the weight of the individual parts is relatively low. However, heavy demands are imposed on the tensioning elements and their anchorages. A standardised manufacture is not possible, since deliveries must be tailored to the project. Usually in a project, many different cable diameters, different lengths and a wide variety of end connections are required, where many vital measurement details (e.g. for the many different short cables) can only be determined shortly before installation.

[0003] Spiral or stranded cables, or else wire cables made from a number of wires arranged in parallel are used as tensioning elements. Said wires arranged in parallel display a higher breaking load than spiral cables and are distinguished by their high fatigue resistance (known as endurance limit) and a high modulus of elasticity (without the need for an expensive, time-consuming stretching process carried out on special tractive machines). They are anchored at each end in an end piece absorbing the tensile forces exerted on the wire cable, with the end connection being made by an expensive wedge anchorage of individual wires. This type of anchorage device, which is highly complex in its structure, is disclosed for example in the generic DE-A-34 37 107.

[0004] The present invention on the other hand was based on the problem of creating a tensioning element which is simple in terms of technical installation and economical, of the type mentioned at the beginning, which enables rapid anchorage of the wire cable in the end piece and nevertheless guarantees a high breaking load.

[0005] This problem is solved according to invention by the fact that the end piece is provided at least in part with a plastic deformable sheath serving to accommodate one end of a wire cable, where this sheath can be compressed with the end of the wire cable.

[0006] Further preferred designs of the tensioning element according to invention form the object matter of the sub-claims.

[0007] It was, surprisingly, determined in the tensioning element according to invention that the transfer of the tensile forces exerted by the wire cable on the end piece is guaranteed just as completely as those in wedge anchorages known in the art, and a very high breaking load is achieved with this tensioning element.

[0008] In this case the loss of breaking load due to plastic deformation is only 5%, which is less than the so-called spinning loss in spiral or stranded cables, which usually amounts to a breaking load reduction of approx. 10%. The spinning loss does not apply to straight wires. For a specified breaking load therefore the tensioning element becomes lighter and also cheaper.

[0009] However, the manufacture of the tensioning element according to invention is also simpler, not only because the winding and spinning procedures are omitted, but also due to the fact that no stretching procedure is necessary to achieve a necessary modulus of elasticity, especially, though, due to the simple type of anchorage. This enables simple project-oriented manufacture and rapid deliverability.

[0010] The invention is explained below in more detail on the basis of the drawings, which show:

[0011]FIG. 1 a part of a tensioning element according to invention in lateral view,

[0012]FIG. 2 a cross section through the tensioning element according to FIG. 1 along the line II-II, and

[0013]FIG. 3 a partial view of a bridge using tensioning elements according to invention.

[0014] According to FIG. 1 and FIG. 2 a tensioning element 1 according to invention includes a wire cable 2, which consists of a number of straight wires 3 arranged in parallel. Depending on the required breaking load, there will be at least seven, or again, anything up to several hundred wires 3. The material used is a steel which is galvanised or coated with zinc/aluminium or similar, chrome nickel steel or aluminium so that no additional corrosion protection is necessary. Obviously, too, wires made from high-strength steel with a nominal strength of approx. 1800 N/mm² can also be used.

[0015] Preferably the wire cable 2 will be bundled from wires 3 of the same diameter (e.g. 2 or 3 mm), as the result of which enormous logistical and manufacturing advantages arise (less stockholding, less residual quantities or even waste, lower purchase price, faster delivery dates, etc.). For the production of the wire cable 2, in a way not shown in more detail, a wire 3 is drawn through a straightener during pay-out from a wire coil in order to obtain a completely straight form. Next, the wires are each individually cut into sections. The wires thus prepared are then bundled such that a wire cable 2 with a circular cross section is formed. As can be seen from FIG. 2, this causes slight gaps 3′ to form, but these cause no problem and do not effect any reduction in breaking load. When bundling is precise, in principle, more of a hexagonal cross section will be formed.

[0016] In order to retain the round cross sectional shape of the wire cable 3 over its entire length, a number of retaining rings 4, 5 are provided, arranged at a distance from each other and distributed over the entire length, only two of which can be seen from FIG. 1. The distance will depend on the wire diameter and/or the number of wires and is between 500 and 2000 mm.

[0017] Another option, not visible from the drawing, for the retention of the round cross sectional form would be banding made from virtually any material (paper, plastic, round wire, flat wire, etc.). These could potentially offer a new architectural design field.

[0018] The wire cable 3 is anchored with its wire cable end in a borehole 7 of the end piece 6 or end fitting, which is connected with a corresponding building component and which absorbs the tensile forces exerted on the wire cable, and transfers them to the building component (obviously the other end of the wire cable, not visible from FIG. 1, is similarly anchored in another end piece). For the connection with the building component the end piece 6 or its part 6 a can for example be provided with a thread, or else designed as a conventional connection piece with a lug, a fork or other connection element.

[0019] For the anchorage, the end piece 6 is provided with a plastic deformable sheath 6 b, in the borehole 7 of which the equally round end of the wire cable is inserted, and held in a frictional connection by radial constriction of the sheath 6 b. The ratio of the length of the cylindrical clamping area formed by the sheath hole to the external diameter of the wire cable 2 optimally lies between 4 and 8. Thus for example with a diameter of the wire cable of 16 mm, the length of the clamping area of the sheath hole will be selected as 90 to 100 mm.

[0020] In FIG. 2, the plastic deformations 9 on the inner side of the sheath 6 b are shown for illustration purposes. Obviously the wires can also deform, when compressed, to a certain extent.

[0021] As already mentioned, the use of wires of a single diameter is especially advantageous, although different diameters could also be used.

[0022] Due to the inapplicability of spinning losses and the small reduction in breaking load in the anchorage of the end of the wire cable by compression of the end piece sheaths, this same strength can be achieved with thin or higher tensile strength wires.

[0023] The simple manufacture of the tensioning element according to invention (no winding or spinning processes, no stretching procedure, simple anchorage of the wire cable ends in the end pieces) is advantageous, not only with respect to costs, but it also brings with it great flexibility, i.e. the option of a rapid, project-based production. Also important are the stock-related advantages; it is no longer necessary to hold stocks of diverse cables.

[0024] According to FIG. 3, the tensioning elements 1 according to invention are especially suitable as stay cables or bridle chords for a cable-stayed bridge 30, which in this case is shown in diagrammatic form in partial illustration. Such a bridge 30 displays a deck 31, one or more vertical supporting pillars 33, anchored for example on the bed of a river 38 or similar, and a number of tensioning elements 1 with wire cables 2 consisting of wires. At the ends the tensioning elements 1 are held and tensioned in anchorages 35 laterally connected with the bridge, which is not explained in more detail, since these anchorages are designed in conventional fashion. In any case, these end fittings 6 are less massive in comparison with those according to the state of the art and can therefore be kept in an aesthetically pleasing relationship to the other parts. Also shown is a bridge rail 36.

[0025] The invention is sufficiently explained by the above explanations. It could, however, be illustrated by further variants. Thus these tensioning elements are suitable for all kinds of applications, especially architectural, either as supporting elements or else as such for tensioning elements in railings or similar. The end pieces could in principle consist completely of a deformable sheath. 

1. Tensioning element, especially for the suspension of building components, with a number of wires (3) arranged approximately in parallel forming a wire cable (2), the ends of said wires each being anchored in an end piece (6) absorbing the tensile forces exerted on the wire cable (2), characterised in that the end piece (6) is provided at least partially with a plastic deformable sheath (6 b) serving to accommodate one end of a wire cable, where this sheath (6 b) can be compressed with the end of the wire cable.
 2. Tensioning element according to claim 1, characterised in that the wire cable (2) is formed from a number of wires (3), preferably between seven and several hundred, arranged in parallel with each other, displaying a straight form.
 3. Tensioning element according to claim 1 or 2, characterised in that the wires (3) made from high-strength steel can be used to a nominal strength of approx. 1800 N/mm².
 4. Tensioning element according to one of claims 1 to 3, characterised in that the wires (3) are bundled in such a way that a wire cable (2) with an approximately circular cross section is formed, where means (4, 5) to maintain the round cross section over the entire length of the wire cable (2) are provided.
 5. Tensioning element according to claim 4, characterised in that the means consist of retaining rings (4, 5) spaced apart from each other, distributed over the entire length of the wire cable (2).
 6. Tensioning element according to claim 4, characterised in that the means are formed by banding.
 7. Tensioning element according to one of the claims 4 to 6, characterised in that the sheath (6 b) housing the end of the wire cable having a round cross section is radially compressible in the plastic deformation.
 8. Tensioning element according to one of claims 1 to 7, characterised in that the wire cable (2) is formed from wires (3) displaying the same diameter.
 9. Tensioning element according to one of claims 1 to 7, characterised in that the tensioning element (1) is provided as a stay cable or bridle chord for a cable-stayed bridge.
 10. Method of manufacture of a tensioning element according to one claims 1 to 9, characterised in that for the production of the wire cable (2) the wire (3) is drawn through a straightener during pay-out from a wire coil in order to obtain a straight form, that the wires (3) are next stretched, preferably individually, and thereafter bundled together into a wire cable (2), which is then compressed at the ends with an end piece (6).
 11. Method of manufacture of a tensioning element according to claim 10, characterised in that the wire cable (2) is formed into an approximately circular cross section. 